Method of forming fine patterns of semiconductor device by using double patterning process which uses acid diffusion

ABSTRACT

A method of forming fine patterns of a semiconductor device according to a double patterning process that uses acid diffusion is provided. In this method, a plurality of first mask patterns are formed on a substrate. A capping film including an acid source is formed on the exposed surface areas of the plurality of first mask patterns. A second mask layer is formed on the capping films. A plurality of acid diffused regions are formed within the second mask layer by diffusing acid obtained from the acid source from the capping films into the second mask layer. A plurality of second mask patterns are formed of residual parts of the second mask layer which remain after removing the acid diffused regions of the second mask layer.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 12/267,687, now allowed, filed on Nov. 10, 2008, which claimspriority to Korean Patent Application No. 10-2008-0041483, filed on May2, 2008, in the Korean Intellectual Property Office, the disclosures ofwhich are incorporated herein in their entireties by reference.

BACKGROUND

The present invention relates to a method of forming fine patterns of asemiconductor device, and more particularly, to a method of forming finepatterns of a semiconductor device, by which fine patterns arerepeatedly formed at intervals of a fine pitch by using a doublepatterning process, thereby overcoming a resolution limit of existingexposure equipment.

Forming fine patterns is essential in manufacturing highly-integratedsemiconductor devices. In order to integrate many elements within asmall area, the size of the individual elements needs to be minimized.In order to form small elements, a pitch corresponding to a sum of thewidth of each pattern to be formed and an interval between adjacentpatterns should be designed to be small. With the recent rapid reductionin design rules of semiconductor devices, there is a limit in formingdesired fine-pitch patterns due to a resolution limit inphotolithography for forming patterns required to manufacturesemiconductor devices. In particular, in a photolithographic process forforming line and space patterns on a substrate, there is a limit informing desired fine-pitch patterns due to a resolution limit.

In order to overcome the resolution limits in such photolithographicprocesses, some methods of forming fine hard mask patterns having finepitches by using a double patterning process have been proposed.However, according to these methods of forming fine mask patterns byusing the double patterning process, a material used to form the finemask patterns needs to be deposited within an aperture having a highaspect ratio according to a deposition process such as chemical vapordeposition (CVD). Therefore, there is a limit in forming a film havinggood burying characteristics, namely, having no defects such as voids,within the aperture.

SUMMARY

The present invention provides a method of forming fine patterns of asemiconductor device using a double patterning process, by which etchmask patterns are formed with a doubled density within a predeterminedarea by using a chemical reaction without using expensive depositionequipment.

According to an aspect of the present invention, there is provided amethod of forming fine patterns of a semiconductor device. In thismethod, a plurality of first mask patterns are formed on a substrate sothat the plurality of first mask patterns may be equally separated fromone another respectively by a first space, in a direction parallel to amain surface of the substrate. A capping film comprising an acid sourcemay be formed on side walls and an upper surface of each of theplurality of first mask patterns. A second mask layer may be formed onthe capping films so as to fill the first spaces. A plurality of aciddiffused regions extending from the capping films into the second masklayer may be formed by diffusing acid obtained from the acid source fromthe capping films into the second mask layer. A plurality of second maskpatterns corresponding to residual parts of the second mask layer whichremain in the first spaces after removing the acid diffused regions ofthe second mask layer may be formed.

Each of the capping films may further include water-soluble polymer. Theacid source may include a water-soluble acid or potential acid.

The acid source may include a first photoacid generator that includes achromophore group and generates acid when being exposed to a laser, forexample, a KrF excimer laser (248 nm), an ArF excimer laser (193 nm), oran F₂ excimer laser (157 nm). The acid source may include a thermoacidgenerator.

The second mask layer may include neither acid nor potential acid, i.e.,the second mask layer may be devoid of an acid or potential acid. Thesecond mask layer may include an inactive acid source different than theacid source included in the capping film. The inactive acid source mayinclude a second photoacid generator that includes no chromophoregroups, generates no acid when being exposed to a KrF excimer laser (248nm), an ArF excimer laser (193 nm), or an F₂ excimer laser (157 nm), andgenerates acid when being exposed to extreme ultraviolet (EUV) light (1to 31 nm). Alternatively, the inactive acid source may include a firstphotoacid generator that includes a chromophore group and generates acidwhen being exposed to a laser, for example, a KrF excimer laser (248nm), an ArF excimer laser (193 nm), or an F₂ excimer laser (157 nm).

The second mask layer may include a photoresist film which includes apolymer having an acid-labile group and includes neither acid norpotential acid.

In the forming of the acid diffused regions, a resultant substrate onwhich the second mask layer has been formed may be thermally treated soas to diffuse the acid obtained from the acid source from the cappingfilms into the second mask layer.

When the acid source includes a first photoacid generator comprising achromophore group, the forming of the acid diffused regions may includegenerating a first acid from the acid source contained in the cappingfilms by exposing the resultant substrate on which the second mask layerhas been formed on the capping films, and diffusing the first acid fromthe capping films into the second mask layer by thermally treating aresultant substrate on which the first acid has been generated. When theacid source includes a thermoacid generator, the forming of the aciddiffused regions may include generating a second acid from the acidsource contained in the capping films by thermally treating theresultant substrate on which the second mask layer has been formed onthe capping films, and diffusing the second acid from the capping filmsinto the second mask layer.

The acid diffused regions may be developed using a basic aqueoussolution in order to be removed from the second mask layer.

When the plurality of first mask patterns includes a photoresist film,the method may further include the operation of hardening the pluralityof first mask patterns so that the plurality of first mask patterns haveinsolubility with respect to an organic solvent. Such operation occursbetween the forming of the plurality of first mask patterns and theforming of the second mask layer. The hardening of the plurality offirst mask patterns may be performed before or after the capping filmsare formed.

The method may further include etching the substrate by using theplurality of first mask patterns and the plurality of second maskpatterns as an etch mask.

According to another aspect of the present invention, there is provideda method of forming fine patterns of a semiconductor device. In thismethod, a plurality of first mask patterns are formed on a substrate. Acapping film including an acid source including acid, a first photoacidgenerator having a chromophore group, or a thermoacid generator may beformed on exposed surface areas of each of the plurality of first maskpatterns. A second mask layer may be formed on the capping films,wherein the second mask layer includes polymer having an acid-labilegroup and a second photoacid generator not having a chromophore group. Aplurality of acid diffused regions within the second mask layer may beformed by diffusing acid obtained from the acid source from the cappingfilms into the second mask layer. A plurality of second mask patternscorresponding to residual parts of the second mask layer which remainafter removing the acid diffused regions of the second mask layer may beformed.

According to another aspect of the present invention, there is provideda method of forming fine patterns of a semiconductor device. In thismethod, a plurality of first mask patterns are formed on a substrate. Acapping film may be formed on exposed surface areas of each of theplurality of first mask patterns, wherein the capping film includes anacid source including acid, a first photoacid generator having achromophore group, or a thermoacid generator. A second mask layer may beformed on the capping films, wherein the second mask layer includespolymer having an acid-labile group and includes neither acid norpotential acid. A plurality of acid diffused regions may be formedwithin the second mask layer by diffusing acid obtained from the acidsource from the capping films into the second mask layer. A plurality ofsecond mask patterns corresponding to residual parts of the second masklayer which remain after removing the acid diffused regions of thesecond mask layer may be formed.

According to another aspect of the present invention, there is provideda method of forming fine patterns of a semiconductor device. In thismethod, a plurality of first mask patterns are formed on a substrate. Acapping film may be formed on exposed surface areas of each of theplurality of first mask patterns, wherein the capping film includes anacid source including one of acid and a thermoacid generator. A secondmask layer may be formed on the capping films, wherein the second masklayer includes a polymer having an acid-labile group and a firstphotoacid generator having a chromophore group. A plurality of aciddiffused regions may be formed within the second mask layer by diffusingacid obtained from the acid source from the capping films into thesecond mask layer. A plurality of second mask patterns corresponding toresidual parts of the second mask layer which remain after removing theacid diffused regions of the second mask layer may be formed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1G are cross-sectional views illustrating a method offorming fine patterns of a semiconductor device, according to anexemplary embodiment of the present invention;

FIG. 2 is a flowchart illustrating operations that can be implemented insome specific cases, in the fine pattern forming method illustrated inFIGS. 1A through 1G, according to an embodiment of the presentinvention; and

FIG. 3 is a flowchart illustrating operations that can be implemented inother specific cases, in the fine pattern forming method illustrated inFIGS. 1A through 1G, according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will now be described more fully with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown. The invention may, however, be embodied in manydifferent forms and should not be construed as being limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the concept of the invention to those skilled in the art. In thedrawings, the thicknesses of layers and regions are exaggerated forclarity. Like reference numerals in the drawings denote like elements.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Like numbers refer to like elementsthroughout. As used herein the term “and/or” includes any and allcombinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother element, component, region, layer or section. Thus, a firstelement, component, region, layer or section discussed below could betermed a second element, component, region, layer or section withoutdeparting from the teachings of the present invention.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Furthermore, relative terms such as “below,” “beneath,” or “lower,”“above,” and “upper” may be used herein to describe one element'srelationship to another element as illustrated in the accompanyingdrawings. It will be understood that relative terms are intended toencompass different orientations of the device in addition to theorientation depicted in the accompanying drawings. For example, if thedevice in the accompanying drawings is turned over, elements describedas being on the “lower” side of other elements would then be oriented on“upper” sides of the other elements. Similarly, if the device in one ofthe figures is turned over, elements described as “below” or “beneath”other elements would then be oriented “above” the other elements.Therefore, the exemplary terms “below” and “beneath” can, therefore,encompass both an orientation of above and below.

FIGS. 1A through 1G are cross-sectional views illustrating a method offorming fine patterns of a semiconductor device, according to anexemplary embodiment of the present invention.

Referring to FIG. 1A, a to-be-etched film 110 is formed on a substrate100, and a plurality of first mask patterns 120 are formed on theto-be-etched film 110. The first mask patterns 120 are equally separatedfrom one another respectively by a first space S1 in a directionsubstantially parallel to a main surface of the substrate 100.

The substrate 100 may be a silicon substrate.

The to-be-etched film 110 may be formed of any material according to thepurposes of patterns that are to be formed on the to-be-etched film 110.If a gate electrode is formed on the substrate 100, the to-be-etchedfilm 110 may be a conductive layer, for example, a doped polysiliconlayer, or a stacked structure including the doped polysilicon layer anda metal silicide layer. If bit lines are formed on the substrate 100,the to-be-etched film 110 may be formed of a metal, for example,tungsten or aluminum. If fine patterns to be finally formed are formedby etching the substrate 100, the to-be-etched film 110 may not beformed. For example, if active regions are defined in the substrate 100by using a method according to the present invention, the to-be-etchedfilm 110 may be omitted. In some cases, before the first mask patterns120 are formed on the to-be-etched film 110, an antireflective film (notshown) may be further formed on the to-be-etched film 110.

The first mask patterns 120 may be resist patterns formed of a typicalresist composition. In order to form the first mask patterns 120, forexample, a resist film may be formed by coating an upper surface of theto-be-etched film 110 with a photoresist material, and then the resistfilm may undergo exposure and development according to a typicalphotolithographic process so as to form resist patterns havingapertures. The apertures may expose portions of the upper surface of theto-be-etched film 110; the portions having predetermined widths.

For example, the first mask patterns 120 may be formed of a chemicalamplification positive resist composition that includes a photoacidgenerator (PAG). In this regard, the first mask patterns 120 may beformed of a resist composition for a KrF excimer laser (248 nm), aresist composition for a ArF excimer laser (193 nm), or a resistcomposition for an F₂ excimer laser (157 nm). Alternatively, the firstmask patterns 120 may be formed of a negative resist composition. Whenthe first mask patterns 120 are formed of a negative resist composition,the first mask patterns 120 may be formed of a combination of athermoacid generator (TAG), in which acid decomposition of the TAGoccurs at a temperature higher than a process temperature used until thefirst mask patterns 120 are formed, with the negative resistcomposition. Reasons for and effects of the formation of the first maskpatterns 120 by using the mixture of the TAG and the negative resistcomposition will be described later with reference to FIG. 1E.

Referring to FIG. 1B, a capping film 130 is formed on sidewalls and anupper surface of each of the first mask patterns 120.

Each of the capping films 130 includes an acid source comprising acid orpotential acid. For example, each of the capping films 130 may be formedof a mixture of a polymer and an acid source.

The potential acid included in the capping films 130 may be, forexample, perfluorobutane sulfonic acid (C₄F₉SO₃H), trifluoroacetic acid(CF₃CO₂H), or trifluoromethanesulfonic acid (CF₃SO₃H).

Alternatively, the potential acid included in the capping films 130 maybe a first PAG which includes a chromophore group and generates acidwhen being exposed to laser, such as a KrF excimer laser (248 nm), anArF excimer laser (193 nm), or a F₂ excimer laser (157 nm). In thiscase, the first PAG may be formed of triarylsulfonium salts,diaryliodonium salts, sulfonates, or a mixture of two or more of thesematerials. For example, the first PAG may be triphenylsulfoniumtriflate, triphenylsulfonium antimonate, diphenyliodonium triflate,diphenyliodonium antimonate, methoxydiphenyliodonium triflate,di-t-butyldiphenyliodonium triflate, 2,6-dinitrobenzyl sulfonates,pyrogallol tris(alkylsulfonates), N-hydroxysuccinimide triflate,norbornene-dicarboximide-triflate, triphenylsulfonium nonaflate,diphenyliodonium nonaflate, methoxydiphenyliodonium nonaflate,di-t-butyldiphenyliodonium nonaflate, N-hydroxysuccinimide nonaflate,norbornene-dicarboximide-nonaflate, triphenylsulfoniumperfluorobutanesulfonate, triphenylsulfonium perfluorooctanesulfonate(PFOS), diphenyliodonium PFOS, methoxydiphenyliodonium PFOS,di-t-butyldiphenyliodonium triflate, N-hydroxysuccinimide PFOS, ornorbornene-dicarboximide PFOS, or a mixture of two or more of thesecompounds.

Alternatively, the potential acid included in the capping films 130 maybe a TAG that generates acid by heat. The TAG may be formed of analiphatic or alicyclic compound. For example, the TAG may be formed ofat least one compound of carbonate ester, sulfonate ester, and phosphateester. More specifically, the TAG may be formed of at least one compoundof cyclohexyl nonafluorobutanesulfonate, norbornylnonafluorobutanesulfonate, tricyclodecanyl nonafluorobutanesulfonate,adamantyl nonafluorobutanesulfonate, cyclohexylnonafluorobutanecarbonate, norbornyl nonafluorobutanecarbonate,tricyclodecanyl nonafluorobutanecarbonate, adamantylnonafluorobutanecarbonate, cyclohexyl nonafluorobutanephosphonate,norbornyl nonafluorobutanephosphonate, tricyclodecanylnonafluorobutanephosphonate, or adamantyl nonafluorobutanephosphonate ora mixture of two or more of these compounds.

When the capping films 130 are formed of a mixture of polymer and theacid source, the content of the acid source may be 0.01 to 50% by weightbased on a gross weight of the polymer.

Polymer that may be included in the capping films 130 may bewater-soluble polymer. For example, the water-soluble polymer mayinclude at least one of an acrylamide type monomer unit, a vinyl typemonomer unit, an akylenglicol type monomer unit, a maleic anhydridemonomer unit, an ethylenimine monomer unit, a monomer unit comprising anoxazoline group, an acrylonitrile monomer unit, an allylamide monomerunit, a 3,4-dihydropyran monomer unit, and a 2,3-dihydrofuran monomerunit, as a repeating unit.

A method of forming the capping films 130 may comprise a process ofcoating exposed surfaces of the first mask patterns 120 with a cappingcomposition composed of a mixture of water, water-soluble polymer, andan acid source composed of water-soluble acid or potential acid and thenthermally treating the resultant coated first mask patterns 120.

Another method of forming the capping films 130 may comprise a processof mixing a Resolution Enhancement Lithography Assisted by ChemicalShrink (RELACS™) material (manufactured by AZ Electronic Materials) withone of the aforementioned acid sources, spin-coating the mixture onexposed surfaces of the first mask patterns 120, and baking theresultant first mask patterns 120 for a predetermined period of time ata predetermined temperature, for example, for about 20 to 70 seconds atabout 100 to 130° C., so as to form the capping films 130. At this time,acid remaining on the surfaces of the first mask patterns 120 may serveas a catalyst, and thus the RELACS™ material may be cross-linked withthe surfaces of the first mask patterns 120, thereby forming the cappingfilms 130. After the capping films 130 are formed, an unnecessarycoating composite remaining on the capping films 130 may be removed bywater, an organic solvent, a mixture of water and an organic solvent, ora developing solution.

Referring to FIG. 1C, the first mask patterns 120 are hardened so as tohave insolubility with respect to an organic solvent, for example,propylene glycol methyl ether acetate (PGMEA), ethyl lactate (EL),cyclohexanone, etc.

The first mask patterns 120 may be hardened by a plasma treatment 135.Plasma in the plasma treatment 135 may be, for example, Ar plasma or HBrplasma.

Although the plasma treatment 135 is performed after the formation ofthe capping films 130 in the present embodiment, the inventive conceptis not limited thereto. That is, the plasma treatment 135 may beperformed between the formation of the first mask patterns 120 and theformation of the capping films 130. When the capping films 130 containthe first PAG or acid, the solubility of the first mask patterns 120with respect to an organic solvent may be changed even by onlyperforming a baking process after the coating of the first mask patterns120 with a coating composition in order to form the capping films 130.Thus, in a subsequent process (for example, a process of forming thesecond mask layer 140, described below with reference to FIG. 4D), thefirst mask patterns 120 may become insoluble with respect to an organicsolvent used when the capping films 130 are coated with another resistmaterial, and thus dissolution of the first mask patterns 120 may beprevented.

Referring to FIG. 1D, a second mask layer 140 is formed on the cappingfilms 130 and the to-be-etched film 110 so as to fill the first spacesS1 between the first mask patterns 120.

The second mask layer 140 may be a photoresist film. The photoresistfilm that forms the second mask layer 140 may be a photoresist film thatincludes neither an acid nor a potential acid and includes a polymerhaving an acid-labile group.

Alternatively, the second mask layer 140 may include an inactive acidsource different from the aforementioned acid source. The inactive acidsource may be composed of potential acid. For example, the second masklayer 140 may be formed of a photoresist film that includes a polymerhaving an acid-labile group and the potential acid. In this case, thepotential acid included in the second mask layer 140 may comprise asecond PAG which has no chromophore groups, generates no acid when beingexposed to one of a KrF excimer laser (248 nm), an ArF excimer laser(193 nm), and a F₂ excimer laser (157 nm), and generates acid when beingexposed to an extreme ultraviolet (EUV) light (1 to 31 nm).

The second PAG may be composed of a material expressed in one ofFormulas 1 and 2.

wherein:

R₁, R₂, and R₃ denote alkyl groups of C₁˜C₁₀;

X denotes an alicyclic hydrocarbon group of C₃˜C₂₀ which forms a ringtogether with S⁺ of Formula 2, and at least one CH₂ in the alicyclichydrocarbon group can be substituted with one of S, O, N, a ketonegroup, and R₅—S⁺A⁻ (where R₅ denotes an alkyl group of C₁˜C₁₀;

R₄ denotes an alkyl group of C₁˜C₂₀, a cycloalkyl group of C₁˜C₂₀, analicyclic hydrocarbon group of C₁˜C₂₀, an aromatic hydrocarbon group ofC₁˜C₂₀, a hydroxyl group, a cyano group, a nitro group, or ahalogen-family element;

n denotes 0 or 1;

R₂ and R₃ in Formula 1 may form rings in cooperation with S⁺ of Formula1 and thus can be combined with each other in the form of —R₂—R₃— so asto be expressed as Formula 2 when n=0; and

A⁻ denotes a counter ion.

For example, the second PAG may be comprised of trimethylsulfoniumtriflate, methyl-tetrahydrothiophene triflate,methyl-pentahydrothiopyran triflate, methyl-tetrahydrothiopyran-4-onetriflate, or methyl-dithiane triflate.

In some cases, the potential acid included in the second mask layer 140may be composed of the first PAG, which includes a chromophore group andgenerates acid when being exposed to a laser such as a KrF excimer laser(248 nm), an ArF excimer laser (193 nm), or a F₂ excimer laser (157 nm).In this case, an exposure of the second mask layer 140 should not beperformed until the second mask layer 140 is removed.

Although it is illustrated in FIG. 1D that the second mask layer 140 maybe formed to have an upper surface higher than the upper surfaces of thecapping films 130, the present invention is not limited to thisformation. For example, the second mask layer 140 may be formed to havea height less than or equal to that of the upper surface of each of thecapping films 130, by being partially solved using a developing solutionor an organic solvent (for example, alcohol liquid).

Although not illustrated in FIG. 1D, after the formation of the secondmask layer 140, an upper capping film (not shown) or an acid supplylayer (not shown) comprising the same material as a material used toform the capping films 130 may be further formed on the upper surface ofthe second mask layer 140. A detailed description of this case will nowbe made with reference to FIG. 1E.

Referring to FIG. 1E, acid obtained from the acid source included in thecapping films 130 is diffused into the second mask layer 140, therebyforming acid diffused regions 142 which extend from the capping films130 into the second mask layer 140.

The acid diffused regions 142 may be formed by exposure or thermaltreatment.

A case where the acid diffused regions 142 are formed by exposurecorresponds to a case where the acid source included in the cappingfilms 130 is the first PAG. The case where the acid diffused regions 142are formed by exposure may be applied only when the second mask layer140 comprises a photoresist film including polymer having an acid-labilegroup and includes neither acid nor potential acid or when the secondmask layer 140 comprises a photoresist film including polymer having anacid-labile group and includes an inactive acid source, that is, thesecond PAG which has no chromophore groups and generates no acid whenbeing exposed to a KrF excimer laser (248 nm), an ArF excimer laser (193nm), or a F₂ excimer laser (157 nm).

When the acid diffused regions 142 are formed by exposure, a resultantsubstrate on which the second mask layer 140 has been formed may beexposed to a laser such as a KrF excimer laser (248 nm), an ArF excimerlaser (193 nm), or an F₂ excimer laser (157 nm) so as to generate acidfrom the first PAG, and a resultant substrate on which acid has beengenerated from the capping films 130 is thermally treated so as todiffuse the acid existing within the capping films 130 into the secondmask layer 140. The thermal treatment may be performed at a temperatureof about 25 to 200° C. The time required for the thermal treatment maybe variably controlled according to a desired distance by which acid isdiffused.

A case where the acid diffused regions 142 are formed by thermaltreatment corresponds to a case where the acid source included in thecapping films 130 is acid or a TAG. In this case, since exposure is notperformed when the second mask layer 140 has been formed on thesubstrate 100, the second mask layer 140 may be formed of a photoresistfilm including polymer having an acid-labile group, and the first PAGthat includes a chromophore group and generates acid when being exposedto a KrF excimer laser (248 nm), an ArF excimer laser (193 nm), or a F₂excimer laser (157 nm) may be included in the second mask layer 140.When the first PAG is included within the second mask layer 140, thesecond mask layer 140 is not exposed. Thus, the first PAG continuouslymaintains an inactive state in which acid is not generated. In addition,the second mask layer 140 may include neither acid nor potential acid,or include an inactive acid source which generates no acid when beingexposed to a KrF excimer laser (248 nm), an ArF excimer laser (193 nm),or an F₂ excimer laser (157 nm), like the second PAG.

When the acid diffused regions 142 are formed by thermal treatment, aresultant substrate on which the second mask layer 140 has been formedmay be thermally treated so as to consecutively 1) perform a process ofgenerating acid from the TAGs included in the capping films 130 and 2) aprocess of diffusing the acid existing within the capping films 130 intothe second mask layer 140.

In the formation of the first mask patterns 120 described above withreference to FIG. 1A, when the first mask patterns 120 are formed of anegative type resist composition which is mixed with a TAG in which aciddecomposition occurs at a temperature higher than a process temperatureused until the first mask patterns 120 are formed, a resultant substrateon which the second mask layer 140 has been formed may be thermallytreated at a temperature equal to or greater than a temperature at whichthe TAG included in the first mask patterns 120 generates acid, and thusacid is generated from the TAG included in the first mask patterns 120.While the acid included in the capping films 130 is being diffused intothe second mask layer 140, the acid included in the first mask patterns120 may also be diffused into the second mask layer 140. The generationof acid from the TAG included in the first mask patterns 120 and thethermal treatment for the diffusion of the acid may be performedsimultaneously with the generation of acid from the TAG included in thecapping films 130 and the thermal treatment for the diffusion of theacid, respectively.

If an acid source composed of the second PAG not including a chromophoregroup, which is expressed as Formula 1 or 2, is included in the secondmask layer 140, when the acid from the capping films 130 is diffusedinto the second mask layer 140, the second PAG adjacent to the aciddiffused into the second mask layer 140 may act as acid withoutundergoing exposure. Accordingly, when the second PAG exists in thesecond mask layer 140, the size of the acid diffused regions 142increases compared with when no second PAGs exist in the second masklayer 140. A detailed description of the increase of the size of theacid diffused regions 142 will now be made with reference to thefollowing experiment.

Within the acid diffusion region 142 of the second mask layer 140, aprotecting group of polymer included in the second mask layer 140 isde-protected by the acid diffused from only the capping films 130 or theacid diffused from both the first mask patterns 120 and the cappingfilms 130, and thus the second mask layer 140 turns into a state solublein a developing solution.

Although not shown in FIG. 1E, when the upper capping film (not shown)or the acid supply layer (not shown) comprises the same material as thematerial used to form the capping films 130 and is further formed on theupper surface of the second mask layer 140 after the formation of thesecond mask layer 140 as described above with reference to FIG. 1D, notonly acid obtained from the acid source included in the capping films130 but also acid obtained from the upper capping film may be diffusedinto the second mask layer 140 so that upper acid diffused regions (notshown) extending a predetermined depth from the upper surface of thesecond mask layer 140 may be formed, not only around the first maskpatterns 120, but also in the upper portion of the second mask layer140.

Referring to FIG. 1F, the acid diffused regions 142 of the second masklayer 140 are removed. Consequently, a plurality of second mask patterns140A corresponding to residual portions of the second mask layer 140 maybe formed within the first spaces S1.

In order to remove the acid diffused regions 142 of the second masklayer 140, a process of developing the acid diffused regions 142 may beperformed. The process may include using a basic aqueous developingsolution, for example, a solution of tetramethyl ammonium hydroxide(TMAH) of 2.38% by weight.

Referring to FIG. 1G, fine patterns 110A are formed by etching theto-be-etched film 110 by using the first mask patterns 120 and thesecond mask patterns 140A as an etch mask.

After the formation of the fine patterns 110A, portions of the firstmask patterns 120 and the second mask patterns 140A remaining on thefine patterns 110A may be removed. The remaining portions of the firstmask patterns 120 and the second mask patterns 140A may be removed usingan ashing process and a stripping process.

FIG. 2 is a flowchart illustrating operations that can be implementedwhen the second mask layer 140 includes polymer having an acid-labilegroup and the second PAG or when the second mask layer 140 includes thepolymer having an acid-labile group and includes neither the first PAGnor the second PAG, in the fine pattern forming method illustrated inFIGS. 1A through 1G, according to an embodiment of the inventiveconcept.

Referring to FIG. 2, in operations 210 a through 210 d, the first maskpatterns 120, the capping films 130, and the second mask layer 140 areformed on the to-be-etched film 110 on the substrate 100 as describedabove with reference to FIGS. 1A through 1D. Here, the second mask layer140 may include a polymer having an acid-labile group and the secondPAG, or may include the polymer having an acid-labile group and mayinclude neither the first PAG nor the second PAG.

Operations 210 e-1 and 210 e-2 correspond to the formation of the aciddiffused regions 142 described above with reference to FIG. 1E. Theoperation 210 e-1 denotes a process of generating acid from the cappingfilms 130, and the operation 210 e-2 denotes a process of diffusing theacid generated from the capping films 130.

When the acid source included in the capping films 130 is acid, forexample, water-soluble acid, the acid generation process, namely, theoperation 210 e-1, may be omitted, and the operation 210 e-2 may followthe operation 210 d. When the acid source included in the capping films130 is the first PAG, a resultant substrate on which the second masklayer 140 has been formed may be exposed to a laser as provided hereinso as to generate acid from the first PAG of the capping films 130. Onthe other hand, when the acid source included in the capping films 130is a TAG, a resultant substrate on which the second mask layer 140 hasbeen formed may be thermally treated to generate acid from the TAGs ofthe capping films 130.

In operation 210 e-2, a resultant substrate on which acid exists in thecapping films 130 may be thermally treated so as to diffuse the acidexisting in the capping films 130 into the second mask layer 140.

Thereafter, the fine patterns 110A are formed on the substrate 100through the processes described above with reference to FIGS. 1F and 1G.

FIG. 3 is a flowchart illustrating operations that may be implementedwhen the second mask layer 140 includes a polymer having an acid-labilegroup and the first PAG, in the fine pattern forming method illustratedin FIGS. 1A through 1G, according to an embodiment of the inventiveconcept.

Referring to FIG. 3, in operations 310 a through 310 d, the first maskpatterns 120, the capping films 130, and the second mask layer 140 areformed on the to-be-etched film 110 on the substrate 100 as describedabove with reference to FIGS. 1A through 1D. Here, the second mask layer140 may include the polymer having an acid-labile group and the firstPAG.

Operations 310 e-1 and 310 e-2 correspond to the formation of the aciddiffused regions 142 described above with reference to FIG. 1E. Theoperation 310 e-1 denotes a process of generating acid from the cappingfilms 130, and the operation 310 e-2 denotes a process of diffusing theacid generated from the capping films 130. In the present embodiment,since the second mask layer 140 includes the first PAG, exposure may notbe performed after the second mask layer 140 is formed and until thesecond mask layer 140 is removed, in order to prevent acid from beinggenerated from the first PAG. Thus, the capping films 130 may include noPAGs which generate acid during exposure.

In operation 310 e-1, when the acid source included in the capping films130 is acid, for example, a water-soluble acid, the acid generationprocess, namely, the operation 310 e-1, may be omitted, and theoperation 310 e-2 may follow the operation 310 d. When the acid sourceincluded in the capping films 130 is the TAG, a resultant substrate onwhich the second mask layer 140 has been formed may be thermally treatedso as to generate acid from the TAGs of the capping films 130.

In operation 310 e-2, a resultant substrate on which acid exists in thecapping films 130 may be thermally treated so as to diffuse the acidexisting in the capping films 130 into the second mask layer 140.

Thereafter, the fine patterns 110A may be formed on the substrate 100through the processes described above with reference to FIGS. 1F and 1G.

Experiment

As described above with reference to FIG. 1E, if the second mask layer140 includes an acid source composed of the second PAG not including achromophore group, when the acid was diffused from the capping films 130into the second mask layer 140, the second PAG adjacent to the acid maydiffuse into the second mask layer 140 acted as acid without undergoingexposure.

First, an ArF resist layer including acid-labile polymer and a secondPAG composed of trimethylsulfonium triflate was formed on a siliconwafer, and a first sample group which formed a C₄F₉SO₃H acid sourcelayer on the resist layer was manufactured. The first sample groupincludes first samples respectively including 1% by weight of the secondPAG and and 5.0% by weight of the second PAG based on the gross weightof the polymer within the resist layer.

As a comparative, a second sample was manufactured in the same manner asthat of the first sample group except that an ArF resist layer notincluding the second PAG was formed.

The first sample group and the second sample were thermally treated for60 seconds at 100° C. so as to diffuse acid from the acid source layerto the resist layer.

When the first sample group and the second sample had not undergoneexposure, the first sample group and the second sample were developedusing a solution of TMAH of 2.38% by weight, and then the amount of theresist layer removed was measured. As a result, the thicknesses of theresist layers of the first samples removed due to the developing of theresist layers of the first samples, including 1% and 5.0% by weight ofthe second PAGs based on the gross weight of the polymer, were about 280Å and about 667 Å, respectively. In other words, as the amount of thesecond PAG contained in the resist layer of the first sample groupincreases, the amount of the resist layer removed due to the developmentincreases. Meanwhile, the thickness of the resist layer of the secondsample removed due to the developing of the resist layer of the secondsample was about 249 Å.

When the first sample group and the second sample had not undergoneexposure, distances by which the acid from the acid source layer wasdiffused up to the resist layers of the first samples, including 1% and5.0% by weight of the second PAGs based on the gross weight of thepolymer, were about 270 Å and about 659 Å, respectively. Meanwhile, adistance by which the acid from the acid source layer was diffused tothe resist layer of the second sample was about 248 Å.

According to the results of the aforementioned experiment, in the caseof the first sample group, a portion of the second PAG contained in theresist layer, which is adjacent to the acid diffused from the acidsource layer, from among the entire second PAG acts as acid even withoutexecution of exposure, and thus deprotects the protecting group of thepolymer contained in the resist layer.

Thus, in the embodiment described above with reference to FIGS. 1Athrough 1G, when the second PAG is included in the second mask layer140, the size of the acid diffused regions 142 may be enlarged comparedwith when second PAGs are not included in the second mask layer 140.

According to the present invention, in a method of forming fine-pitchpatterns, which are required to manufacture highly-integratedsemiconductor devices, by using a double patterning process, first, aplurality of first mask patterns are formed on a substrate, a cappingfilm including an acid source is formed on exposed surfaces of each ofthe first mask patterns, and a second mask pattern may then be formed inbetween every two adjacent first mask patterns by diffusion of acid fromthe capping films. In this way, the fine-pitch patterns, which overcomea resolution limit generated during photolithography, may be formed.

Furthermore, the density of patterns may be increased by using a methodof arranging a mask pattern in between every two adjacent first maskpatterns according to acid diffusion. Thus, patterns having fine widthsthat are not controlled by a typical process may be formed, the densityof patterns required to manufacture a semiconductor device can beincreased, and various forms of fine patterns can be formed. Therefore,patterns having a fine pitch difficult to achieve in a typicalphotolithographic process may be easily formed.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the inventive concept as defined by the following claims.

What is claimed is:
 1. A method of forming fine patterns of asemiconductor device, the method comprising: forming a plurality offirst mask patterns on a substrate; forming a capping film on exposedsurface areas of each of the plurality of first mask patterns, whereinthe capping film comprises an acid source comprising one of acid, afirst photoacid generator having a chromophore group, and a thermoacidgenerator; forming a second mask layer on the capping film, wherein thesecond mask layer comprises polymer having an acid-labile group and asecond photoacid generator not having a chromophore group; forming aplurality of acid diffused regions within the second mask layer bydiffusing acid obtained from the acid source from the capping film intothe second mask layer; removing the acid diffused regions of the secondmask layer; and forming a plurality of second mask patternscorresponding to residual parts of the second mask layer which remainafter removing the acid diffused regions of the second mask layer. 2.The method of claim 1, wherein: the capping film on exposed surfaces ofeach of the plurality of first mask patterns comprises the firstphotoacid generator as the acid source; and the forming of the aciddiffused regions comprises: generating a first acid from the firstphotoacid generator contained in the capping film by exposing theresultant substrate on which the second mask layer has been formed onthe capping film; and diffusing the first acid from the capping filminto the second mask layer by thermally treating a resultant substrateon which the first acid has been generated.
 3. The method of claim 1,wherein: the capping film on exposed surfaces of each of the pluralityof first mask patterns comprises a thermoacid generator as the acidsource; and the forming of the acid diffused regions comprises:generating a second acid from the thermoacid generator contained in thecapping film by thermally treating the resultant substrate on which thesecond mask layer has been formed on the capping film; and diffusing thesecond acid from the capping film into the second mask layer.
 4. Themethod of claim 1, wherein the acid diffused regions are developed usinga basic aqueous solution in order to be removed from the second masklayer.
 5. A method of forming fine patterns of a semiconductor device,the method comprising: forming a plurality of first mask patterns on asubstrate; forming a capping film on exposed surface areas of each ofthe plurality of first mask patterns, wherein the capping film comprisesan acid source comprising one of acid, a first photoacid generatorhaving a chromophore group, and a thermoacid generator; forming a secondmask layer on the capping film on exposed surfaces of each of theplurality of first mask patterns, wherein the second mask layercomprises polymer having an acid-labile group and comprises neither acidnor potential acid; forming a plurality of acid diffused regions withinthe second mask layer by diffusing acid obtained from the acid sourcefrom the capping film into the second mask layer; removing the aciddiffused regions of the second mask layer; and forming a plurality ofsecond mask patterns corresponding to residual parts of the second masklayer which remain after removing the acid diffused regions of thesecond mask layer.
 6. The method of claim 5, wherein, in the forming ofthe acid diffused regions, a resultant substrate on which the secondmask layer has been formed is thermally treated so as to diffuse theacid obtained from the acid source from the capping film into the secondmask layer.
 7. The method of claim 5, wherein: the capping film onexposed surfaces of each of the plurality of first mask patternscomprises the first photoacid generator as the acid source; and theforming of the acid diffused regions comprises: generating a first acidfrom the first photoacid generator contained in the capping film byexposing the resultant substrate on which the second mask layer has beenformed on the capping film; and diffusing the first acid from thecapping film into the second mask layer by thermally treating aresultant substrate on which the first acid has been generated.
 8. Themethod of claim 5, wherein: the capping film on exposed surfaces of eachof the plurality of first mask patterns comprises a thermoacid generatoras the acid source; and the forming of the acid diffused regionscomprises: generating a second acid from the thermoacid generatorcontained in the capping film by thermally treating the resultantsubstrate on which the second mask layer has been formed on the cappingfilm; and diffusing the second acid from the capping film into thesecond mask layer.
 9. The method of claim 5, wherein: the plurality offirst mask patterns comprise a photoresist film; and between the formingof the plurality of first mask patterns and the forming of the secondmask layer, the method further comprises hardening the plurality offirst mask patterns so that the plurality of first mask patterns haveinsolubility with respect to an organic solvent.
 10. A method of formingfine patterns of a semiconductor device, the method comprising: forminga plurality of first mask patterns on a substrate; forming a cappingfilm on exposed surface areas of each of the plurality of first maskpatterns, wherein the capping film comprises an acid source comprisingone of acid and a thermoacid generator; forming a second mask layer onthe capping film, wherein the second mask layer comprises a polymerhaving an acid-labile group and a first photoacid generator having achromophore group; forming a plurality of acid diffused regions withinthe second mask layer by diffusing acid obtained from the acid sourcefrom the capping film into the second mask layer; removing the aciddiffused regions of the second mask layer; and forming a plurality ofsecond mask patterns corresponding to residual parts of the second masklayer which remain after removing the acid diffused regions of thesecond mask layer.